1. The Field of the Invention
The present invention relates to the field of agriculture, in particular to a system for the disinfection of agricultural soil.
2. The Relevant Technology
The technology for the disinfection of agricultural soil with the use of microwaves or radiofrequency is nowadays well known. Microwave and radiofrequency technologies are potentially much more efficient and economical than steam technology, however, practical use of microwaves to date has been hampered by its severe intrinsic limitations due to the difficulty of efficiently coupling energy to the soil and the poor overall energetic efficiency.
Use of electromagnetic energy to kill soil pathogens has been proposed in several documents, for example U.S. Pat. Nos. 5,287,818, 6,638,475, 7,601,936.
The main drawbacks related to the transfer of radiofrequency or microwave energy to the soil (referred here below as “electromagnetic energy”) are the difficulty of efficiently coupling electromagnetic energy to the soil and the intrinsic limitation to the energetic efficiency of the generation of radiofrequency or microwave energy.
In many practical instances the energy is transported by an agricultural working or tractor system in the form of fuel, therefore the first conversion performed is the one from chemical (fuel) to electric energy, and this is obtained through the use of a suitable transportable power generator. In this case, a further energy loss occurs, in the form of heat, thus worsening the overall performances of the energy conversion.
The difficulty related to the efficient coupling of the electromagnetic energy to the soil is due to the fact that the electromagnetic energy is generated above the soil surface, on the agricultural moving vehicle or working tool, and is coupled to the soil by means of antennas or similar devices.
Hence, a significant fraction of the electromagnetic energy does not penetrate the soil and, in addition, due to soil losses, the energy coupling decreases with depth.
A solution to this problem was set forth in document U.S. Pat. No. 5,287,818, where it was disclosed to generate microwave energy below the soil surface through suitable “microwave generator units”, and the generated energy was coupled to the soil directly by exposure behind “protecting domes”. In that document the way of coupling the microwave energy to the soil was not specified.
The above discussed solution has in principle advantages with respect to solutions wherein above-surface energy generation is performed together with the use of electromagnetic energy coupling devices, but it has also, on the other side, several disadvantages.
First of all, the space available to the microwave generator units is significantly limited, thus limiting the available microwave power and the energy efficiency of such generators.
Secondly, the need to protect the sub-surface microwave generators introduces severe limitations to the mechanical structure of the hosting agricultural working tool and to the efficiency in shaping the microwave energy coupling to the soil.
Therefore, there is the need to have an innovative system for performing a disinfection of an agricultural soil which allows to efficiently coupling the energy to the soil, which can be easily used together with standard agricultural tools and which can perform an accurate disinfection of the soil with high overall energy efficiency.